Patent GB-583116-A (GB)
Title: Improvements relating to the conversion of saturated hydrocarbons into saturated hydrocarbons of more branched chain character
IPC: C07C5/27
Filed: 1943-07-15
Abstract: Saturated aliphatic hydrocarbons are isomerized to others of more branched chain character by maintaining in a vertical reaction zone a static liquid column of catalyst consisting of aluminium halide-aliphatic hydrocarbon complex containing dissolved, but substantially free from undissolved halide and forming a continuous liquid phase, continuously introducing the said hydrocarbons to the lower part of said zone to pass upwardly in dispersed liquid phase through the catalyst in the presence of hydrogen halide and under isomerizing conditions, maintaining the volume of catalyst greater than that of the hydrocarbons under treatment therein, and continuously withdrawing isomerized product from the top of said zone.  An aluminium chloride-aliphatic hydrocarbon complex which gives no sediment on centrifuging at room temperature and which has an absolute heat of hydrolysis of about 213-426, preferably 320-352 calories per gram, is suitable.  The hydrocarbon of the complex may be a petroleum or gasoline hydrocarbon, particularly kerosene.  Thus aluminium chloride, kerosene and hydrogen chloride may be agitated in a closed reactor for 4 hrs. at 210 DEG  F. and the complex phase separated.  Other halides such as the bromide may be used.  For butane, temperatures of 180-240 DEG , and not in excess of 300 DEG F., may be used, with contact times of several seconds to several minutes or more.  The feed is highly dispersed uniformly over the cross-sectional area as by spray discharge upwardly into the lower venturi portion of an unpacked tower filled with the liquid complex, impinging of the spray on the sloping walls being avoided.  Hydrogen chloride up to 5 per cent by weight of the hydrocarbon feed is also injected.  A temperature gradient of 20-50 DEG  F. in the direction of hydrocarbon flow through the catalyst is permissible.  The volume of catalyst to hydrocarbon feed in the tower may be of the order of 2-200.  It may be less than 2, but the hydrocarbon hold-up generally does not exceed 75 per cent by volume of the catalyst.  A drop velocity of 0.1-0.5 ft./sec. is suitable, with droplets of diameter 1/64 -\ba1/4 in.  The depth of catalyst may be from a few feet up to 20 or 40 feet.  The products are conducted to a receiver, where pressure may be released to free gases such as hydrogen chloride which is recycled, and are then fractionated to recover isobutane and n-butane which is recycled.  If its activity decreases, part of the catalyst may be withdrawn intermittently or continuously from the base of the tower and make-up aluminium halide added, for example to the withdrawn catalyst or to the hydrocarbon feed, to maintain the character of the catalyst body. In an example, n-butane with 3 per cent hydrogen chloride at 210 DEG  F. and 335-350 lbs./sq. in. is charged to the base of a 15 ft. tower filled with liquid AlCl3-kerosene complex, the volume p  ratio of complex to butane being about 4 : 1.  Other hydrocarbons which may be treated include pentane, about 150 DEG  F. being a suitable temperature, hexane, at about 100 DEG  F., and a hexane cut containing naphthenes, when temperatures up to 250 DEG  F. may be required.  Prior removal of olefins, aromatics, water and sulphur compounds may be effected.